The present invention relates in general to the art of drilling for oil and gas and more particularly to an improved apparatus for measuring the level of drilling mud in a mud pit.
During the drilling of an oil or gas well, it is important to constantly measure the level of the drilling mud in the mud pits. For example, a change in the volume of mud in the mud pits provides an indication of a potential blowout. In drilling an oil or gas well, high pressure gas from an underground reservoir may enter the wellbore. The entry of the gas is controlled by the pressure exerted by the drilling mud. The intrusion of gas is manifested by the forcing of an equivalent amount of drilling mud out of the wellbore and into the mud pits. The removal of mud from the wellbore decreases the pressure opposite the underground reservoir and allows more gas to enter the wellbore. A blowout can occur when the gas blows a substantial portion of the remaining mud out of the wellbore and the gas itself appears at the surface. Fire and accompanying loss of life and property often results from the uncontrolled blowing of gas at the surface. On the other hand if too much pressure is exerted upon the wellbore while attempting to control the gas, fracturing of the protective casing in the wellbore or the earth formations surrounding the wellbore can occur and the gas will then escape in an uncontrolled manner into the earth formations. This may manifest itself by the gas blowing in an uncontrolled manner around the drilling rig once it has worked its way to the surface. In either case, there is an economic loss including the loss of potential fuel. An accurate and continuous measurement of the level of drilling mud in the mud pits can be used to detect and take action to prevent potential blowouts. This is set out in greater detail in U.S. Pat. No. 3,608,653 to William A. Rehm, patented Sept. 28, 1971.